1. Field of the Invention
The present invention relates to an image forming apparatus having an image correcting function, a control apparatus for controlling the image forming apparatus, and an image forming system including these apparatuses.
2. Description of Related Art
In recent years, image forming apparatuses, such as printers, have been requested to provide higher image quality. Various image correction techniques have therefore been studied in order to stabilize the image output.
In particular, a large variation is found in quality of the images immediately after the restart of the quiescent image formation apparatus. Such a variation should be avoided.
Japanese Patent No. 3854965 (hereinafter referred to as Patent Literature 1) discloses a technique for detecting an image formed on the first sheet after power-up to determine a correction value for an image forming condition, and applying the correction value to image formation on the first sheet after the next power-up.
Japanese Patent Application Laid Open Publication No. 2004-347666 (hereinafter referred to as Patent Literature 2) discloses a technique for detecting a toner image formed on a photoreceptor, acquiring an optimal development condition based on the detection result, correcting the development condition in consideration of a quiescent time period and humidity information at the start of the next image formation, and applying the corrected development condition to the next image formation.
In particular, the quality of the images formed after the restart of the quiescent image forming apparatus is unstable before the stabilization of the image forming apparatus. This instability causes a variation in output of image formation on every sheet. This variation in image quality on every sheet changes with time. More specifically, the degree of variation in image quality between the first sheet and the second sheet is different from that between the second sheet and the third sheet.
The quality of the images formed after the restart of the image forming therefore cannot be readily stabilized before the stabilization of the image forming apparatus.
Both Patent Literatures 1 and 2 involve a technique for correcting an image formed on the second or later sheet after the restart of image formation on the basis of the detection result of the last image formation. In other words, after the restart of the image formation, an image to be formed on the second sheet is processed with a correction value from the detection result of the image on the first sheet, and an image to be formed on the third sheet is processed with a correction value from the detection result of the image on the second sheet.
Unfortunately, as described above, a large variation is found in quality of the images formed on every sheet after the restart of the quiescent image forming apparatus. This variation hinders the production of a desired image corrected on the basis of the detection result of the last image formation.